Systems and methods for intracavitary temperature measurement and monitoring

ABSTRACT

Systems and methods for measuring and monitoring intracavitary tissue temperature. The system may include a catheter shaft with a circuit board disposed therein, the circuit board having an array of sensors disposed thereon. The catheter shaft may have an opening and an expandable structure surrounding the opening to provide a field of view of the intracavitary tissue for the array of sensors through the opening. The system may include a software-based programming system run on a computer such that a clinician may review information indicative of temperature of the intracavitary tissue, and be alerted if the temperature exceeds a predetermined threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/583,798, filed May 1, 2017, now U.S. Pat. No. 10,702,163, whichclaims the benefit of priority of U.S. Provisional Patent ApplicationNo. 62/331,362, filed on May 3, 2016, the entire contents of each ofwhich are incorporated herein by reference.

FIELD OF USE

This application generally relates to systems and methods formeasurement and monitoring intracavitary tissue temperature.

BACKGROUND

Atrial fibrillation (AF) is a major cause of stroke and the most commonarrhythmia that is clinically significant, with prevalence rates of 3.8%in individuals 60 years of age or older and 9.0% in individuals over 80years of age. In 2001, the prevalence of AF was projected to increase2.5-fold by 2050 due to the rapidly growing elderly population. Onesurgical treatment method for AF is called the maze procedure, which wasdeveloped in 1991 by Cox. In this procedure, incisions are made directlyinto the atrium of the heart during major, open heart surgery. Whilesuccessful, due to the procedure's long operative time and morbidityrate, most clinicians have adopted a variation of the procedure whichuses percutaneous radiofrequency ablation (RFA) to create transmurallines of electrically inactive scar tissue within the left atrium (LA),endocardially. As a result, there has been an increase in RFA techniquesto treat paroxysmal and persistent atrial fibrillation. The approach toRFA changed dramatically in 1998 with the discovery by Haïssaguerre andassociates that the majority of ectopic atrial beats originatedsomewhere within 1 or more of the 4 pulmonary veins (PVs) due to theextension of muscular bands from the LA into the PVs. Following thisdiscovery, mapping and ablation of arrhythmogenic foci of both the PVsand the LA have been performed, with today's procedures showing successrates of 60-90%.

Although RFA has been effective at treating atrial fibrillation,complications have been reported, the most serious of which is a leftatrial-esophageal fistula that forms secondary to thermal esophagealinjury. Atrio-esophageal fistula is the most dreadful and lethalcomplication among all others related to AF catheter ablation. Patientswith an atrio-esophageal fistula may be presented with a variety ofsigns and symptoms such as chest pain, heartburn, dysphagia, anorexia,and hematemesis immediately after or also late after the indexprocedure. Usually death occurs because of cerebral or myocardial airembolism, endocarditis, massive gastrointestinal bleeding and septicshock. New esophageal late gadolinium enhancement has been shown to bepresent in almost one-third of patients after AF ablation, suggestingsome form of esophageal injury. This finding is irrespective of the typeof catheter ablation (irrigated vs. not-irrigated tip) used during theprocedure, of ablation time, of anatomical location of the esophaguscompared with the left atrium, of the size of left atrium cavity or ofthe timing of cardiac magnetic resonance study after pulmonary veinisolation.

As demonstrated by computed tomography, cardiac magnetic resonance, andintracardiac echocardiography, the strict anatomic relationship betweenthe left atrium and the esophagus together with the delivery ofradiofrequency energy on the posterior wall of the left atrium are theprincipal causes leading to the occurrence of atrio-esophageal fistulaor, more generally, of esophageal injury.

Since radiofrequency energy exerts a rise in local temperatures, it iscommon practice now to monitor the esophageal temperature with anesophageal probe to titrate the radiofrequency energy application on theareas at potential risk of esophageal injury and to stop radiofrequencyenergy delivery when a rapid elevation of the esophageal internaltemperature is recorded. However, a problem with current systems andmethods for measuring and monitoring intracavitary tissue temperature ispoor correlation between esophageal internal temperature and totalradiofrequency energy delivery.

For example, in U.S. Patent Pub. No. 2014/0012155 to Flaherty, a devicehaving a plurality of sensors is used to monitor temperature ofesophageal tissue while actively ablating target tissue to reduce riskof injury to untargeted tissues. The device may be positioned within theesophagus with positioning elements. However, the accuracy of esophagealtemperature monitoring to estimate the esophageal heating and thenanticipating the formation of the esophageal injury is uncertain. Forexample, particles, fluids and gases traversing the esophagus mayobstruct the field of view of the sensors, resulting in inaccuratetemperature measurements.

It would therefore be desirable to provide improved systems and methodsfor measuring and monitoring intracavitary tissue temperature.

Specifically, it would be desirable to provide systems and methods formeasuring and monitoring intracavitary tissue temperature using a devicetailored for optimal introduction to, positioning at, and having anoptimum, unobstructed field of view of, the target tissue.

SUMMARY

The present invention overcomes the drawbacks of previously-knownsystems by providing systems and methods for measuring and monitoringintracavitary tissue temperature using a device having an expandablestructure that provides optimal field of view of the target tissue,resulting in accurate and early indicators of tissue injury. Forexample, the intracavity tissue may be tissue at the inner wall of abody lumen such as the esophagus so that the systems and methods permitmeasuring and monitoring tissue temperature at the inner wall of thebody lumen.

In accordance with one aspect of the present invention, a system forintracavitary tissue temperature measurement and monitoring is provided.The system may include an introducer device sized and shaped to bepositioned adjacent to an intracavitary tissue and software that runs ona computer operatively coupled to the introducer device.

The introducer device may include a catheter shaft having a distal end,a longitudinal axis, a lumen extending therethrough, and an opening atthe distal end along the longitudinal axis such that at least a portionof the lumen is exposed. The catheter shaft may have a circuit board atleast partially disposed in the opening at the distal end of thecatheter shaft, wherein the circuit board has an array of infraredsensors disposed thereon. The circuit board may be rotated within thecatheter shaft to alter a field of view through the opening of thecatheter shaft. The sensors of the array of infrared sensors may eachhave circuitry integrate therewith that is programmed to generate asignal indicative of temperature of the intracavitary tissue.

The introducer device may also include an expandable structure formedfrom an infrared transmissive material and disposed on the cathetershaft proximal to the opening at the distal end to surround the array ofinfrared sensors, providing a field of view through the opening. Theexpandable structure may be a restrained or unrestrained inflatablebladder providing an optimum viewing distance between the array ofinfrared sensors and the intracavitary tissue. Alternatively, theintroducer device may have a transmissive foil glued or sealed to theedges of the opening of the catheter shaft, thereby providing the arrayof infrared sensors a field of view through the opening.

The non-transitory computer readable media has instructions storedthereon that, when executed by a processor operatively coupled to thecircuit board, cause a graphical user interface to display informationindicative of temperature of the intracavitary tissue based on thesignal from the array of infrared sensors. The instructions stored onthe non-transitory computer readable media may also cause, when executedby the processor, the graphical user interface to trigger an alarm ifthe generated signal indicative of temperature of the intracavitarytissue exceeds a predetermined threshold to alert the patient'sclinician. Accordingly, the clinician may cease or adjust theapplication of RF ablation to nearby tissue to thereby preventesophageal injury.

In accordance with another aspect of the present invention, a method formeasuring and monitoring intracavitary tissue temperature using thesystem described above is provided. First, the clinician positions theintroducer device adjacent to an intracavitary tissue such that theopening of the catheter shaft is oriented toward the intracavitarytissue. The clinician then inflates the bladder to provide a field ofview through the opening and an optimal viewing distance between thearray of infrared sensors and the intracavitary tissue. The clinicianoptionally may rotate, either manually or by a motor, the circuit boardwithin the lumen of the catheter shaft to achieve a desired field ofview of the intracavitary tissue.

Next, the clinician instructs the array of infrared sensors to detectinfrared radiation emitted by the intracavitary tissue. The circuitryintegrated with each sensor of the array of infrared sensors thenprocesses the detected infrared radiation to generate a signalindicative of temperature of the intracavitary tissue. Processing thedetected infrared radiation may include amplifying the signal, filteringthe signal, performing compensation for local actual temperature of theone or more infrared sensors, and converting the signal to a digitalserial stream for convenient use by the clinician's computer.

Finally, the processed information indicative of temperature of theintracavitary tissue based on the generated signal is displayed on agraphical user interface. In addition, the graphical user interface maytrigger an alarm if the generated signal indicative of temperature ofthe intracavitary tissue exceeds a predetermined threshold to alert theclinician so that the clinician may cease or adjust the application ofRF ablation to nearby tissue to thereby prevent esophageal injury.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of an exemplary embodiment of a systemconstructed in accordance with the principles of the present invention.FIG. 1B is a schematic view of an alternative embodiment of a systemconstructed in accordance with the principles of the present invention.

FIG. 2 illustrates the circuit board of FIG. 1A.

FIG. 3A shows a front cross-sectional view of an alternative embodimentof the introducer device of FIG. 1A.

FIG. 3B shows a front cross-sectional view of an alternative embodimentof the introducer device of FIG. 3A having a restrained bladder element.

FIG. 3C shows a front cross-sectional view of the introducer device ofFIG. 3B disposed within an esophagus.

FIGS. 4A and 4B show an alternative embodiment of the introducer deviceof FIG. 1A, where FIG. 4A is a schematic view and FIG. 4B shows a frontcross-sectional view of the alternative embodiment of the introducerdevice.

FIG. 5A shows an alternative embodiment of the introducer device of FIG.4A. FIG. 5B shows an alternative embodiment of the introducer device ofFIG. 5A.

FIGS. 6A and 6B show an alternative embodiment of the introducer devicein accordance with the principles of the present invention, where theintroducer device is in a delivery state in FIG. 6A and in a deployedstate in FIG. 6B.

FIG. 7 illustrates an exemplary method for using the system of FIG. 1Ato measure and monitor intracavitary temperature in accordance with theprinciples of the present invention.

FIGS. 8A to 8D illustrate an exemplary method for manufacturing theexpandable structure of FIG. 1A.

DETAILED DESCRIPTION

The systems and methods of the present invention may provide accuratemeasuring and monitoring of intracavitary tissue temperature byproviding an optimal field of view over a large surface area of theintracavitary tissue. In accordance with the principles of the presentinvention, the systems and methods may be optimized for use in theesophagus to measure and monitor esophageal tissue to effectivelyprevent esophageal injury and atrio-esophageal fistula.

Referring to FIG. 1A, an overview of intracavitary probe system 100 inaccordance with one embodiment of the present invention is provided. InFIG. 1A, components of the system are not depicted to scale on either arelative or absolute basis. Intracavitary probe system 100 comprisesintroducer device 102 and software-based monitoring system 116.

In the illustrated embodiment, introducer device 102 includes cathetershaft 104, circuit board 110, and expandable structure 114. Cathetershaft 104 has distal end 106 adapted to be inserted in a body lumen,e.g., the esophagus, adjacent to an intracavitary tissue, e.g., wall ofbody lumen cavity. Catheter shaft 108 also has a lumen extendingtherethrough for receiving circuit board 110. Catheter shaft 104 mayinclude opening 108 along a longitudinal axis at distal end 106, suchthat opening 108 exposes at least a portion of the lumen of cathetershaft 104, providing a field of view for circuit board 110 disposedtherein. Opening 108 may be formed by cutting out a section of cathetershaft 104 during fabrication of introducer device 102. Circuit board 110may be flexible or rigid, and has array of sensors 112 disposed thereon.Preferably, array of sensors 112 are infrared sensors. Expandablestructure 114 is formed of transmissive material, e.g., infraredtransmissive foil, and shaped and sized to be disposed on distal end 106of catheter shaft 104 to form a “viewing window” for array of sensors112. In one embodiment, array of sensors 112 measures infrared radiationemitted by the intracavitary tissue adjacent to introducer device 102through opening 108 of catheter shaft 104 and expandable structure 114.

Circuit board 110 may be slidably inserted into a lumen of cathetershaft 104 along rails such that array of sensors 112 is exposed fromwithin catheter shaft 104 creating a field of view through opening 108.The rails may be rotatable such that circuit board 110 and array ofsensors 112 may be rotationally positioned about the longitudinal axisof catheter shaft 104 to face the correct direction, e.g., toward theheart, to achieve the desired field of view. Preferably, circuit board110 is rotatable such that array of sensors 112 remains exposed inopening 108 in the rotation range permitted by the rails, whileproviding additional viewing angles. For example, array of sensors 112may be disposed within opening 108 of catheter shaft 104 to create afield of view having a predetermined angle, e.g., less than 180°, lessthan 150°, less than 120°, or less than 90°. Accordingly, circuit board110 housing array of sensors 112 may be rotatable to adjust the angle ofthe field of view to a second, different predetermined angle, e.g.,greater or less than the first predetermined angle. The rails may berotated manually or may be coupled to a motor such that the rails may berotated by the motor operated by the clinician. For example, the railsmay be rotated by any amount up to 360 degrees.

In one embodiment, circuit board 110 may be fixed within catheter shaft104. For example, stiffening wires made of a biocompatible material,e.g., stainless steel or nitinol, may be inserted through catheter shaft104 to prevent circuit board 110 from moving from a desired viewingposition, e.g., facing toward the heart, as described in further detailbelow.

In one embodiment, circuit board 110 may be reusable whereas cathetershaft 104 is disposable. For example, the more expensive circuit boardhaving array of sensors 112 disposed thereon may be removably insertedinto disposable catheter shaft 104 when used by the patient's clinicianfor measuring and monitoring purposes. At the end of the measurement andmonitoring procedure, the disposable catheter shaft, the portion ofintroducer device 102 which contacts the patient's bodily lumen, may bediscarded and circuit board 110 may be inserted into a new disposablecatheter shaft for use with another patient, or the same patient at alater time.

Expandable structure 114 may be made of an infrared transmissivematerial, e.g., a thin film polymer having a thickness in the range of 5micron to 1 mm. In addition, the infrared transmissive material may havetransparency in the relevant wavelength range between 1 to 30 microns,or 4 to 16 microns, or 10 to 15 microns. For applications not requiringan optimal sensitivity or not needing a rapid detection, materials withless specific infrared transmissivity may be used for, e.g., their moresuitable mechanical or physical properties. The space between array ofsensors 112 and expandable structure 114 may be at least partiallycreated by cutting out a section of distal end 106 of catheter shaft 104to create opening 108. In one embodiment, catheter shaft 104 may includea glue lumen and a plurality of holes extending from the glue lumen toan external wall of catheter shaft 104 such that a glue, e.g., adhesivematerial, may be inserted within the glue lumen to affix catheter shaft104 to expandable structure 114, as described in further detail below.

As shown in FIG. 1A, expandable structure 114 may be an inflatablebladder formed of infrared transmissive material. In an inflated state,the bladder may have an ovoid shape or an oval cross section to conformto the inside of a body lumen, e.g., esophagus. Preferably, expandablestructure 114 is formed of a compliant or semi-compliant material. Thebladder may be filled with air or a dry gas, thereby providing space infront of, or surrounding array of sensors 112, such that array ofsensors 112 may see through the air or gas, creating a field of view ofthe adjacent intracavitary tissue so that array of sensors 112 maymeasure the tissue temperature directly. Specifically, array of sensors112 may detect the temperature, e.g., infrared radiation, emitted fromthe intracavitary tissue through expandable structure 114, and throughthe air or gas in the space between array of sensors 112 and expandablestructure 114. For example, the gas may be CO₂, Ar, He, or any othersuitable gas selected based on the required infrared detectionspecificity and/or sensitivity. Alternatively, when there are nospecific clinical requirements, air is preferably used. In addition,upon inflation, the inflatable bladder may provide an optimal viewingdistance, e.g., 2 to 8 mm, between array of sensors 112 and theintracavitary tissue to be measured and monitored. As will be understoodby a person having ordinary skill in the art, expandable structure 114may be inflated via, e.g., a syringe pump, coupled to a proximal end ofcatheter shaft 104.

Software-based monitoring system 116 is installed and runs on acomputer, and is used by the patient's clinician to monitor the measuredtemperature of the intracavitary tissue and/or to control functioning ofintroducer device 102. Preferably, the computer is electrically coupledto circuit board 110 and, thereby, to array of sensors 112. The computermay be a conventional computer such as a desktop, laptop, tablet,smartphone, mobile device, LCD display, or the like or may be anapplication specific computer customized for use with introducer device102. For example, the computer may include a customized housing having adisplay for displaying the measured temperature of the intracavitarytissue and a fluid source in fluid communication with expandablestructure 114 to expand, e.g., inflate, expandable structure 114, andmay permit the clinician to activate expansion and/or a monitoringsession. Introducer device 102 may be coupled, either wirelessly orusing a cable, to the computer such that software-based monitoringsystem 116 may receive data indicative of the temperature of theintracavitary tissue. Software-based monitoring system 116 may benon-transitory computer readable media having instructions storedthereon that, when executed by a processor operatively coupled tocircuit board 110, cause a graphical user interface to display and loginternally information indicative of temperature of the intracavitarytissue based on signals received from array of infrared sensors 112. Theinstructions stored on software-based monitoring system 116, whenexecuted by the processor, may also cause the graphical user interfaceto trigger an alarm if the generated signal indicative of temperature ofthe intracavitary tissue exceeds a predetermined threshold. Such analarm allows the patient's clinician to cease or adjust application ofthermal energy, e.g., RF ablation, to a nearby target tissue.

As shown in FIG. 1B, the computer, e.g., data acquisition box 115, mayinclude communication circuitry 117, e.g., cellular (e.g., 3G, LTE,etc.) chipset, IEEE 802.11 (e.g., WiFi) chipset, Bluetooth chipset, orthe like, for wired and/or wireless communication with additionalcomputers, e.g., display 119. Display 119 may include, for example, adesktop, laptop, tablet, smartphone, mobile device, LCD display, or thelike. In this manner, software-based monitoring system 116 may causedata collected at data acquisition box 115 from introducer device 102 tobe transmitted remotely to display 119 for, for example, display,analysis, and/or storage.

Referring now to FIG. 2, a detailed description of circuit board 110 isprovided. As described above, circuit board 110 may be flexible or rigidand has array of sensors 112 mounted thereon. A flexible circuit boardmay be either the full length of catheter shaft 104, going from aconnector at the proximal end of catheter shaft 104 to the distal end ofcatheter shaft 104, or the flexible circuit board may be long enough tohold array of sensors 112 such that array of sensors 112 are connectedto discrete wires to communicate signals from the flexible circuit boardto the connector. In one embodiment, circuit board 110 is slightlylonger than opening 108. The sensors of array of sensors 112 may bespaced apart along circuit board 112 in a manner so as to maximize thefield of view of the surface area of the intracavitary tissue desired tobe measured and monitored. As will be understood by one of ordinaryskill in the art, array of sensors 112 may be selected from infraredsensitive photodiodes, infrared sensitive transistors, infraredsensitive photocells, and infrared sensitive thermopiles. Preferably,array of sensors 112 includes infrared sensitive thermopiles thatgenerate an output voltage proportional to a local temperaturedifference of the intracavitary tissue. As will also be understood byone of ordinary skill in the art, array of sensors 112 may have more orless than four infrared sensors, e.g., depending on the surface area ofthe intracavitary tissue desired to be measured and monitored.

Each sensor of array of sensors 112 may include integrated circuitry118. In one embodiment, array of sensors 112 detects extremely smallamounts of energy from the infrared radiation input and filters andamplifies the detected energy into a meaningful and useful value viacircuitry 118. Circuitry 118 may conduct signal processing which variesfrom a simple filter/amplifier that outputs an analog value, to a morecomplicated processing system involving circuit temperature compensationand conversion to other formats such as a digital output. For example,circuitry 118 may amplify the signal, filter the signal, performcompensation for local actual temperature of the array of infraredsensors irrespective of the infrared input, and convert the signal to adigital serial stream for convenient use by the clinician's computer.Circuitry 118 may be electrically coupled to the clinician's computersuch that software-based monitoring system 116 may receive dataindicative of the temperature of the intracavitary tissue directly fromarray of sensors 112.

Circuit board 110 may include orientation markers 120. For example,orientation markers 120 may be etched into circuit board 110 andviewable under fluoroscopy. As shown in FIG. 2, orientation markers 120may comprise a large circle and two small circles. Alternatively,orientation markers 120 may comprise any pattern of shapers and/ormarkers easily identifiable under fluoroscopy by the patient's clinicianto ensure proper orientation of circuit board 110.

Referring now to FIG. 3A, an alternative exemplary embodiment ofintroducer device 100 is provided. Introducer device 102′ is constructedsimilarly to introducer device 102 of FIG. 1A, wherein like componentsare identified by like-primed reference numbers. Thus, for example,catheter shaft 104′ in FIG. 3A corresponds to catheter shaft 104 of FIG.1A, circuit board 110′ in FIG. 3A corresponds to circuit board 110 ofFIG. 1A, array of sensors 112′ in FIG. 3A corresponds to array ofsensors 112 of FIG. 1A, etc. As shown in FIG. 3A, expandable structure115 may be an unrestrained pillow shaped inflatable bladder having aflat width with catheter shaft 104′ and array of sensors 112′ disposedin opening 108′ along catheter shaft 104′. Specifically, theunrestrained pillow shaped inflatable bladder may completely encapsulatecatheter shaft 104′ including opening 108′ to thereby provide a field ofview of the intracavitary tissue to array of sensors 112′. In oneembodiment, catheter shaft 104′ may include a glue lumen and a pluralityof holes extending from the glue lumen to an external wall of cathetershaft 104′ such that a glue, e.g., adhesive material, may be insertedwithin the glue lumen to affix catheter shaft 104′ to one side of theunrestrained pillow shaped inflatable bladder, e.g., the side adjacentthe dorsal side of the esophagus. The unrestrained pillow shapedinflatable bladder may have fixed dimensions upon inflation with an airor gas as described above. Alternatively, the unrestrained pillow shapedinflatable bladder may have dimensions that change upon inflation basedon infusion pressure of the air or gas within the bladder.

Opening 108′ provides array of sensors 112′ with field of view FOV byexposing at least a portion of array of sensors 112′, such that thefield of view depends on the geometry of opening 108′. For example, awider opening provides a wider field of view of a larger surface area ofthe target intracavitary tissue, and a narrow opening provides anarrower field of view of a smaller surface area of the targetintracavitary tissue. As described above, circuit board 110′ along witharray of sensors 112′ may be rotated via rotatable rails within thelumen of catheter shaft 104′, thereby changing the field of view. Therotation of array of sensors 112′ allows proper orientation in a desireddirection toward the target portion of the intracavitary tissue to bemeasured and monitored.

As shown in FIG. 3A, the unrestrained pillow shaped inflatable bladdermay be inflated such that it has an ovoid shape or an oval cross sectionto conform to the inside of a body lumen, e.g., esophagus. Theunrestrained pillow shaped inflatable bladder may provide an optimalviewing distance, e.g., 2 to 8 mm, between array of sensors 112′ and theintracavitary tissue to be measured and monitored. The inflation of theunrestrained bladder may be pressure controlled such that the bladderstops inflating when it conforms to the body lumen or cavity. Forapplication in an esophagus, the bladder's conformity to the naturallyoval shape of the esophagus facilitates the orientation of introducerdevice 102′ and array of sensors 112′ with the intracavitary tissue tobe measured and monitored. In addition, the oval shape of the inflatedbladder may prevent the esophagus from being pushed out of its normalanatomical position in the patient's body. For example, the esophaguswould not be pushed toward the heart during intracavitary temperaturemeasurement and monitoring, thereby avoiding the risk of reducing thetissue-thickness between the esophagus and the heart's atria which wouldincrease the risk of thermal damage to the esophagus during RF ablationof the atrial tissue. In one embodiment, the unrestrained inflatablebladder may be shaped so that when it is inflated, the bladder may causethe esophagus to pull away from the heart. As will be understood by oneof ordinary skill in the art, the unrestrained inflated bladder may haveother shapes including a spherical shape, a cylindrical shape, or adumbbell shape depending on the application.

Referring to now to FIG. 3B, introducer device 102″ is constructedsimilarly to introducer device 102 of FIG. 1A, wherein like componentsare identified by like-primed reference numbers. Thus, for example,catheter shaft 104″ in FIG. 3B corresponds to catheter shaft 104 of FIG.1A, circuit board 110″ in FIG. 3B corresponds to circuit board 110 ofFIG. 1A, array of sensors 112″ in FIG. 3B corresponds to array ofsensors 112 of FIG. 1A, etc. As shown in FIG. 3B, expandable structure117 may be a restrained pillow shaped inflatable bladder. The restrainedbladder of FIG. 3B may operate in a similar manner to the unrestrainedbladder of FIG. 3A. For example, the inflation of the restrained bladdermay be pressure controlled, the restrained bladder may be inflated withan air or a dry gas, the restrained bladder may provide an optimalviewing distance, e.g., 2 to 8 mm, between array of sensors 112″ and theintracavitary tissue to be measured and monitored, etc.

In addition, the restrained pillow shaped inflatable bladder may beshaped similar to the unrestrained bladder of FIG. 3A on one side of therestrained bladder, e.g., the side adjacent the ventral side of theesophagus facing the heart, whereas the other side, e.g., the sideadjacent the dorsal side of the esophagus, is restrained, therebycreating communication channel 122 running along the longitudinal axisof catheter shaft 104″ between the proximal end and the distal end ofexpandable structure 117. Communication channel 122 may be formed as arecess between catheter shaft 104″ and expandable structure 117. Forexample, expandable structure 117 may not completely encapsulatecatheter shaft 104″, leaving the bottom portion of catheter shaft 104″exposed to engage with the intracavitary tissue, e.g., the dorsal sideof the esophagus as shown in FIG. 3C. Specifically, expandable structure117 may be disposed on catheter shaft 104″ such that it encapsulatesopening 108″ to provide a field of view of the intracavitary tissue, butdoes not encapsulate the bottom portion of catheter shaft 104″. As such,expandable structure 117 conforms with the body lumen in front ofopening 108″ and curves inward toward catheter shaft 104″ on oppositesides of catheter shaft 104″, thereby creating communication channel122. Communication channel 122 may facilitate the displacement of airand liquids on the dorsal side of the body lumen or cavity, e.g.,esophagus, while maintaining full continuous temperature measurement onthe ventral side of the body lumen or cavity. For example, forapplications in esophagus E as shown in FIG. 3C, communication channel122 may be adjacent to the dorsal side of the esophagus, whereas arrayof sensors 112″ have a field of view on the ventral side of theesophagus facing the heart. In addition, as will be understood by one ofordinary skill in the art, the shape of the restrained bladder is notlimited to a pillow shape.

The restrained bladder may include reinforcement features, e.g., wires,straps, flaps, etc., mounted on or behind the backside of the restrainedbladder adjacent to the exposed portion of catheter shaft 104″ toimprove mechanical stability of introducer device 102″, e.g.,push-ability, catheter shaft advancement, rotational positioning, etc.The reinforcement features may assist the formation of communicationchannel 122. As will be understood by one of ordinary skill in the art,the present invention is not limited to application in the esophagus andmay be used for, e.g., measurement of the colon surface during prostatesurgery and/or ablation.

Referring now to FIGS. 4A and 4B, another embodiment of introducerdevice 102 is described. Introducer device 102′″ is constructedsimilarly to introducer device 102 of FIG. 1A, wherein like componentsare identified by like-primed reference numbers. Thus, for example,catheter shaft 104′″ in FIGS. 4A and 4B corresponds to catheter shaft104 of FIG. 1A, circuit board 110′″ in FIGS. 4A and 4B corresponds tocircuit board 110 of FIG. 1A, array of sensors 112′″ in FIGS. 4A and 4Bcorresponds to array of sensors 112 of FIG. 1A, etc. As will be observedby comparing FIGS. 4A and 4B with previous embodiments, introducerdevice 102′″ may include transmissive material 124, e.g., infraredtransmissive foil, that creates the “viewing window” for array ofsensors 112′″ by being coupled to catheter shaft 104′″ over opening108′″ rather than an expandable structure. Transmissive material 124encloses the space between array of sensors 112′″ and transmissivematerial 124 and may be made of an infrared transmissive material, e.g.,a thin film polymer having a thickness in the range of 5 micron to 1 mm.In addition, infrared transmissive material 124 may have transparency inthe relevant wavelength range between 1 to 30 microns, 4 to 16 microns,or 10 to 15 microns. As described above, for applications not requiringan optimal sensitivity or not needing a rapid detection, materials withless specific infrared transmissivity may be used for, e.g., their moresuitable mechanical or physical properties. The space between array ofsensors 112′″ and transmissive material 124 may be at least partiallycreated by cutting out a section of distal end 106′″ of catheter shaft104′″ to create opening 108′″, and covering opening 108′″ by sealing orgluing transmissive material 124 to the edges of opening 108′″.

Referring now to FIG. 5A, another embodiment of introducer device 102 isdescribed. Introducer device 502 is constructed similarly to introducerdevice 102′″ of FIG. 4A. For example, circuit board 510 in FIG. 5Acorresponds to circuit board 110′″ in FIG. 4A, array of sensors 512 inFIG. 5A corresponds to array of sensors 112′″ in FIG. 4A, transmissivematerial 524 in FIG. 5A corresponds to transmissive material 124 in FIG.4A, etc. As will be observed by comparing FIG. 5A with previousembodiments, catheter shaft 504 may include wire lumen 506 and gluelumen 516. A stiffening wire(s) made of, e.g., stainless steel ornitinol, may be inserted through lumen 506 of FIG. 5A to prevent circuitboard 510 from moving after circuit board 510 has been positioned in itsdesired location, e.g., facing the ventral side of the esophagus. Thestiffening wire(s) may also keep the orientation of circuit board 510planar within catheter shaft 504. Alternatively or additionally, thestiffening wire(s) may be inserted within cavity 514 of catheter shaft504.

Catheter shaft 504 may be encapsulated by an unrestrained pillow shapedinflatable bladder. Accordingly, glue lumen 516 of FIG. 5A may haveholes 518 extending therefrom to the external wall of catheter shaft 504along the longitudinal axis of catheter shaft 504, thereby connectingglue lumen 516 with the external wall of catheter shaft 504. Holes 518may include a plurality of holes spaces apart along the longitudinalaxis of catheter shaft 504 or may be one single elongated hole. As such,a glue, e.g., adhesive material, may be inserted within glue lumen 516of FIG. 5A, and exit via holes 518, such that catheter shaft 504 may beaffixed to one side of the unrestrained pillow shaped inflatablebladder, e.g., the side adjacent the dorsal side of the esophagus.

Referring now to FIG. 5B, another embodiment of introducer device 502 isdescribed. Introducer device 502′ is constructed similarly to introducerdevice 502 of FIG. 5A, wherein like components are identified bylike-primed reference numbers. Thus, for example, wire lumen 506′ inFIG. 5B corresponds to wire lumen 506 in FIG. 5A, circuit board 510′ inFIG. 5B corresponds to circuit board 510 in FIG. 5A, array of sensors512′ in FIG. 5B corresponds to array of sensors 512 in FIG. 5A, gluelumen 516′ in FIG. 5B corresponds to glue lumen 516 in FIG. 5A, holes518′ in FIG. 5B corresponds to holes 518 in FIG. 5A, transmissivematerial 524′ in FIG. 5B corresponds to transmissive material 524 inFIG. 5A, etc. Accordingly, catheter shaft 504′ may be encapsulated by anunrestrained pillow shaped inflatable bladder such that a glue may beinserted within glue lumen 516′ of FIG. 5B, and exit via holes 518′,such that catheter shaft 504′ may be affixed to one side of theunrestrained pillow shaped inflatable bladder, e.g., the side adjacentthe dorsal side of the esophagus.

As will be observed by comparing FIG. 5B with FIG. 5A, wire lumen 506′may be positioned below a center line of catheter 502′, e.g., toward thedorsal side of the esophagus. Accordingly, array of electrodes 512′ maybe spaced farther apart from transmissive material 524′ when comparedwith array of electrodes 512 and transmissive material 524 of FIG. 5A,such that opening 508′ may be larger than opening 508.

Referring now to FIGS. 6A and 6B, an alternative embodiment ofintroducer device 602 is described. Introducer device 602 is constructedsimilarly to introducer device 102 of FIG. 1A, wherein like componentsare identified by like-primed reference numbers. Thus, for example,catheter shaft 604 in FIGS. 6A and 6B corresponds to catheter shaft 104of FIG. 1A, opening 608 in FIGS. 6A and 6B corresponds to opening 108 ofFIG. 1A, circuit board 610 in FIGS. 6A and 6B corresponds to circuitboard 110 of FIG. 1A, etc. As shown in FIGS. 6A and 6B, introducerdevice 602 may have support members 624. Each support member 624 has endportions 626 and 630, and middle portion 628. End portions 626 and 630of support members 624 are coupled to the ends of catheter shaft 604adjacent to the proximal and distal ends of opening 608 such that middleportion 628 is parallel to the longitudinal axis of catheter shaft 604in a delivery state as shown in FIG. 6A, and curved outwardly away fromcatheter shaft 604 to engage the intracavitary tissue in a deployedstate as shown in FIG. 6B. As middle portion 628 of support members 624curves outwardly away from catheter shaft 604 as introducer device 602transitions from the delivery state to the deployed state, end portion630 causes the portion of catheter shaft 604 coupled to end portion 630to move over circuit board 610 toward end portion 626. In thisembodiment, a transmissive material covering opening 608 may create afield of view for the array of sensors. As will be understood by one ofordinary skill in the art, introducer device 602 may have more or lessthan two support members 624. For example, introducer device 602 mayhave three or more support members 624.

Referring now to FIG. 7, exemplary method 700 for using the system ofFIG. 1A to measure and monitor intracavitary temperature in accordancewith the principles of the present invention is provided. At 702, theclinician positions introducer device 102 adjacent to an intracavitarytissue to be measured and monitored, e.g., esophageal tissue, such thatopening 108 of catheter shaft 104 is oriented toward the intracavitarytissue. As described above, circuit board 110 may be slidably insertedinto the lumen of catheter shaft 104 along rotatable rails. As such,circuit board 110 may be slidably inserted into the lumen of cathetershaft 104 after introducer device 102 has been positioned adjacent tothe intracavitary tissue. Alternatively, circuit board 110 may beslidably inserted and fixed within catheter shaft 104 prior to thepositioning of introducer device 102 adjacent to the intracavitarytissue.

At 704, the clinician inflates expandable structure 114, e.g.,unrestrained or restrained pillow shaped inflatable bladder describedabove, to provide array of sensors 112 a field of view of the portion ofthe intracavitary tissue to be measured and monitored through opening108, transmissive expandable structure 114, and the air or gas used toinflate expandable structure 114 therebetween. In addition, inflatingexpandable structure 114 provides an optimal viewing distance betweenarray of sensors 112 and the intracavitary tissue.

At 706, the clinician optionally rotates circuit board 110 within thelumen of catheter shaft 104 to achieve a desired field of view of theportion of the intracavitary tissue to be measured an monitored. Theclinician may rotate circuit board 110 within a range of 360 degreesabout the longitudinal axis of catheter shaft 104 in either direction,e.g., clockwise or counter-clockwise. The physician may rotate circuitboard 110 manually or via a motor coupled to the rails. In addition, theclinician may adjust circuit board 110 along the longitudinal axis ofcatheter shaft 104 by sliding circuit board 110 along the rails toassist in achieving the desired field of view of the intracavitarytissue. In an embodiment where the catheter shaft includes one or morewire lumens, a stiffening wire may be inserted within the one or morewire lumens to prevent the circuit board from moving after beingpositioned in the desired location.

At 708, clinician instructs array of sensors 112 to detect the infraredradiation emitting from the intracavitary tissue. At 710, integratedcircuitry 118 of each infrared sensor of array of sensors 112 processesthe detected infrared radiation to generate a signal indicative oftemperature of the intracavitary tissue. Processing the detectedinfrared radiation may include amplifying the signal, filtering thesignal, performing compensation for local actual temperature of the oneor more infrared sensors, and converting the signal to a digital serialstream for convenient use by the clinician's computer. The generatesignal is then received by the clinician's computer either wirelessly orby a cable coupled to both circuit board 110 and the clinician'scomputer.

At 712, the information indicative of temperature of the intracavitarytissue based on the generated signal may be displayed on a graphicaluser interface. In addition, at 714, an alarm may be triggered on thegraphical user interface to alert the clinician or the patient if thegenerated signal indicative of temperature of the intracavitary tissueexceeds a predetermined threshold. As a result, the clinician may adjustoperations, e.g., reduce RF ablation of atrial tissue so as to avoidinjuring the intracavitary tissue, thereby preventing, for example,esophageal injury and/or atrio-esophageal fistula.

Referring now to FIGS. 8A-D, an exemplary method for manufacturing anexpandable structure, e.g., a bladder, is described. As shown in FIG.8A, tube 800 may be provided for manufacturing the expandable structure.Tube 800 may be formed of a thin, flexible, infrared-transmissivematerial, e.g., high-density polyethylene (HDPE) or other materialshaving similar properties, such that tube 800 may be expanded andcontracted. Preferably, tube 800 is formed of a compliant orsemi-compliant material. Tube 800 is shaped and sized to at leastpartially encapsulate an introducer device as described above, and mayhave a lumen extending therethrough having, e.g., a circularcross-sectional area.

As shown in FIG. 8B, the expandable structure is stamped out of tube 800by sealing tube 800 via a sealing machine. For example, sealing of tube800 may be achieved by applying a heating plate on portion 802 of tube800. As will be understood by a person having ordinary skill in the art,any commercially available sealing machine may be used to seal tube 800.The heating plate will apply heat to portion 802 to form mid-portion808, conical portion 804, and straight end portion 806 of the expandablestructure, such that the lumen of tube 800 extends continuously throughmid-portion 808, conical portion 804, and end portion 806. As shown inFIG. 8B, heat may be applied by a heating plate to an upper portion anda lower portion of portion 802 of tube 800, or heat may be appliedcircumferentially around portion 802. As heat is applied to portion 802,the cross-sectional area of tube 800 at mid-portion 808, changes from afirst cross-sectional shape, e.g., a circular cross-sectional shape, toa second cross-sectional shape, e.g., an oval cross-sectional shape.Advantageously, heat applied to conical portion 804 and end portion 806causes mid-portion 808 to change cross-sectional shape from the firstshape to the second shape without the need to apply the heating plate tomid-portion 808. The cross-sectional shape of end portion 806 may becircular or oval in shape, and is preferably sized and shaped to receivea catheter shaft of the introducer device described herein. Sealed tube800 having mid-portion 808, conical portion 804, and end portion 806 isillustrated in FIG. 8C.

As shown in FIG. 8D, the excess materials are cut off end portion 806 ofsealed tube 800 to form one end of the expandable structure havingmid-portion 808, conical portion 804, and remaining end portion 806. Theabove described method steps may be applied to another portion of tube800 simultaneously or at a different time, a predetermined distance fromend portion 806 such that mid-portion 808 has a desirable length for theapplications described herein, thereby forming the other end of theexpandable structure to form a complete expandable structure. FIG. 8Dshows forming conical portion 804 and end portion 806 of two separateexpandable members. The expandable members may have a shape such as thatshown in FIG. 3A.

While various illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true scope of the invention.

What is claimed:
 1. A device for esophageal tissue temperaturemeasurement and monitoring during an atrial tissue ablation procedure,the device comprising: a catheter shaft comprising a lumen and a distalregion configured to be introduced into an esophagus, the catheter shaftfurther comprising an opening at the distal region; an expandablestructure formed of infrared transmissive material and disposed on thedistal region of the catheter shaft over the opening such that theopening is in fluid communication with an interior of the expandablestructure; and a circuit board comprising an array of infrared sensors,the circuit board disposed within the lumen of the catheter shaft suchthat the array of infrared sensors is exposed in the opening, creating afield of view of esophageal tissue through the opening for receivinginfrared radiation emitted by the esophageal tissue.
 2. The device ofclaim 1, wherein the expandable structure is configured to be restrainedupon inflation such that the expandable structure provides acommunication channel between an exterior surface of the expandablestructure and an inner surface of the esophagus.
 3. The device of claim2, wherein the communication channel is configured to facilitatedisplacement of fluid on a dorsal side of the esophagus, whilepermitting continuous temperature measurement on a ventral side of theesophagus.
 4. The device of claim 2, wherein the expandable structurecomprises a reinforcement feature configured to reinforce thecommunication channel between the exterior surface of the expandablestructure and the esophageal tissue.
 5. The device of claim 1, whereinthe expandable structure is an inflatable bladder configured to beinflated with air.
 6. The device of claim 5, wherein the inflatablebladder is configured to be inflated in a pressure controlled mannerwithin the esophagus such that the esophagus is not moved from itsnormal anatomical position relative to a heart.
 7. The device of claim1, wherein the circuit board is configured to be slidably insertedwithin the lumen of the catheter shaft, the circuit board furtherconfigured to be rotated within the lumen of the catheter shaft toenhance the field of view.
 8. The device of claim 1, wherein the circuitboard is further configured to be fixed within the lumen of the cathetershaft.
 9. The device of claim 1, wherein each of the infrared sensorshas circuitry configured to generate a signal indicative of temperatureof the esophageal tissue.
 10. The device of claim 9, wherein thecircuitry is configured to generate the signal indicative of temperatureof the esophageal tissue by amplifying the signal, filtering the signal,performing compensation for temperature of the array of infraredsensors, and converting the signal to a digital serial stream.
 11. Thedevice of claim 9, further comprising software operatively coupled tothe circuit board configured to cause a graphical user interface todisplay information indicative of temperature of the esophageal tissuebased on the signal from the array of infrared sensors.
 12. The deviceof claim 11, wherein the software is configured to cause the graphicaluser interface to trigger an alarm if the generated signal indicative oftemperature of the esophageal tissue exceeds a predetermined threshold.13. The device of claim 1, wherein the array of infrared sensorscomprises at least one of infrared sensitive photodiodes, infraredsensitive transistors, infrared sensitive photocells, or infraredsensitive thermopiles.
 14. The device of claim 1, wherein the circuitboard further comprises one or more orientation markers configured to beviewable under fluoroscopy.
 15. The device of claim 1, wherein theexpandable structure comprises an inflatable bladder having an ovalcross section configured to conform to an inside of the esophagus.
 16. Amethod for measuring and monitoring esophageal tissue temperature duringan atrial tissue ablation procedure, the method comprising: introducinga distal region of a catheter shaft into an esophagus, the distal regionof the catheter shaft comprising an opening, an expandable structuredisposed thereon over the opening such that the opening is in fluidcommunication with an interior of the expandable structure, and acircuit board comprising an array of infrared sensors positioned withinthe lumen of the catheter shaft such that the array of infrared sensorsis exposed in the opening; orienting the opening of the catheter shafttoward target esophageal tissue; expanding the expandable structure toprovide a field of view of the target esophageal tissue through theopening and the expandable structure; and receiving infrared radiationemitted by the target esophageal tissue via the array of infraredsensors.
 17. The method of claim 16, further comprising rotating thecircuit board within the lumen of the catheter shaft to achieve adesired field of view.
 18. The method of claim 16, further comprisingdetecting infrared radiation of the target esophageal tissue from thearray infrared sensors, and processing the detected infrared radiationvia a circuitry coupled to the array of infrared sensors to generate asignal indicative of temperature of the target esophageal tissue. 19.The method of claim 18, further comprising displaying informationindicative of temperature of the target esophageal tissue based on thegenerated signal on a graphical user interface.
 20. The method of claim19, further comprising adjusting the atrial tissue ablation procedurebased on the information indicative of temperature of the targetesophageal tissue to avoid esophageal injury.
 21. The method of claim18, wherein processing the detected infrared radiation via the circuitryto generate a signal indicative of temperature of the target esophagealtissue comprises: amplifying the signal; filtering the signal;performing compensation for temperature of the array of infraredsensors; and converting the signal to a digital serial stream.
 22. Themethod of claim 18, further comprising triggering an alarm on agraphical user interface if the generated signal indicative oftemperature of the target esophageal tissue exceeds a predeterminedthreshold.
 23. The method of claim 16, wherein the expandable structureis an inflatable bladder, and wherein expanding the expandable structurecomprises inflating the inflatable bladder to conform to an inside ofthe esophagus.